Makindo Medical Notes

Related Subjects: |Dementias |Abbreviated Mental Test Score (AMTS) |Alzheimer disease |Dementia with Lewy bodies |Frontotemporal dementia |Corticobasal degeneration |Creutzfeldt Jakob disease |Vascular Dementia |Primary progressive aphasia |Anti Dementia Drugs |AIDS Dementia Complex |Normal Pressure Hydrocephalus |Acetylcholinesterase inhibitors |Mental Capacity Act 2005 |Behavioural and Psychological Symptoms of Dementia

Corticobasal degeneration (CBD) is a rare neurodegenerative disease, classified as a form of adult-onset parkinsonism, often presenting with unilateral arm rigidity, dystonia, and cognitive decline. It is increasingly recognized as part of the spectrum of frontotemporal lobar degeneration.

About

• Also known as Corticobasal ganglia degeneration (CBGD).
• Characterized by a combination of movement disorder, cognitive dysfunction, and language impairment, often with the hallmark alien limb phenomenon (where a limb seems to act independently of the person’s control).
• Classified as a tauopathy, sharing pathological features with other disorders like progressive supranuclear palsy (PSP) and frontotemporal dementia (FTD).

Aetiology

• A tauopathy: Accumulation of tau protein in neurons and glia, leading to neurodegeneration.
• Involves multiple brain regions:
  • Nigrostriatal tracts.
  • Subcortical structures including the thalamus, subthalamic nuclei, pallidum, red nucleus, and dentate nucleus.
  • Pathological changes such as large, pale, ballooned neurons are seen in the basal ganglia.

Clinical Features

• Unilateral parkinsonism: Initially presents on one side with rigidity, bradykinesia, and tremors (although tremors are less common than in idiopathic Parkinson’s disease).
• Alien limb phenomenon: An arm or leg moves involuntarily, performing complex movements without conscious control.
• Dystonia: Involuntary muscle contractions, typically in the affected limb, leading to abnormal postures. The hand often assumes a dystonic posture with wrist and thumb flexed into the palm.
• Myoclonus: Sudden, brief, involuntary muscle jerks, especially in the arms and legs.
• Supranuclear gaze palsy: Difficulty with voluntary eye movements, especially in horizontal and vertical directions, similar to progressive supranuclear palsy (PSP).
• Cognitive and speech issues:
  • Aphasia: Difficulty with speech production or comprehension (often progressive non-fluent aphasia).
  • Dysphasia: Impairment of language ability, affecting communication.
  • Apraxia: Difficulty in performing purposeful movements, even though the desire and physical ability to do so are intact.
  • Dementia: Progressive cognitive decline with memory, reasoning, and personality changes.
  • Behavioral changes including disinhibition, depression, and emotional blunting.
• Asymmetrical presentation of motor symptoms is common, progressing over time to affect both sides.
• Additional signs: postural instability, falls, dysphagia, and sensory deficits.

Investigations

• Blood tests: FBC, U&E, ESR, CRP, LFT, TFT, B12, folate to exclude metabolic and systemic causes.
• Imaging:
  • MRI: Shows asymmetric frontoparietal cortical atrophy (particularly contralateral to the affected side). Cortical thinning and enlarged sulci in parietal and frontal lobes may also be seen.
  • PET scan: Reduced fluorodopa uptake in the basal ganglia. FDG-PET may show asymmetric hypometabolism, particularly in the parietal lobe.
  • DaTscan (SPECT): May help distinguish between corticobasal degeneration and other causes of parkinsonism.
• Neuropsychological tests: Can assess cognitive function and identify deficits in memory, language, and executive function.
• Genetic testing may be performed if there is suspicion of other neurodegenerative diseases (though CBD is not typically genetic).

Management

• Supportive care is the cornerstone of management, with an interdisciplinary approach involving neurologists, physiotherapists, speech therapists, and occupational therapists to help maintain function and independence.
• Medications:
  • L-Dopa: Response to levodopa is usually poor or transient, unlike idiopathic Parkinson’s disease.
  • Quetiapine or other antipsychotics may be used to manage behavioral symptoms such as agitation or delusions, but regular reviews are necessary to minimize cognitive side effects.
  • Dystonia treatments: Clonazepam, valproate, baclofen, or botulinum toxin may help with dystonic postures and movements, though these treatments should be used cautiously to avoid cognitive side effects.
  • Selective serotonin reuptake inhibitors (SSRIs) may be used to manage depression.
• Physiotherapy and regular exercise programs can help maintain mobility and reduce rigidity.
• Speech therapy is important for managing dysphasia and swallowing difficulties, and PEG tubes may be needed in severe cases of dysphagia.
• End-of-life care planning is crucial, focusing on quality of life, symptom management, and addressing dysphagia, immobility, and cognitive decline.

Prognosis

• The disease progresses slowly but steadily, leading to significant disability.
• Median survival is approximately 6-8 years after symptom onset, though progression varies between individuals.
• Death typically results from complications such as pneumonia, infections, or immobility-related issues.